The second graph shows similar upward trends in Alaska. (Credit: Berkeley Lab)

The researchers link this to rising CO2 levels from fossil fuel emissions.Radiative forcing measures how the planet’s energy balance is altered by atmospheric changes. Positive radiative forcing occurs when the Earth absorbs more energy from solar radiation than it emits as heat radiation back to space.“We see, for the first time in the field, the amplification of the greenhouse effect because there’s more CO2 in the atmosphere to absorb what the Earth emits in response to incoming solar radiation,” says Daniel Feldman.Dr Feldman is a scientist in Berkeley Lab’s Earth Sciences Division and is lead author of the paper.